Rhythm tempo control system



April 19, 1966 R. H. CAMPBELL, JR

RHYTHM TEMPO CONTROL SYSTEM Filed Aug. 17, 1962 5 SheetsSheet 1 46g 47 35 as OFF 1 METRONOIIRAIE TZ ST TO ORGAN WESTERIL VOICING 34 CHA A ASSEMBLY BEGINE TANGO MIN. FULL SLOW FAST VOLUME TEMPO 3| i 44 K Wfiam' BOX ooooooooo CODE MATRIX 1 COMM8UTATOR ND 49 48 L AAMS INPUTS OUT OUTPUTS TONE GENERATOR MOTOR CONTROL =15 PHASE -|5O Su MANUAL CONTROL 52 54 PEDAL SWITCH 53 FOX-TROT FIG. 3

WALTZ mn BASS DRUM z R-ToM TOMS INVENTOR' E W|RE BRUSH RICHARD H. CAMPBELL JR.

ATTO RN EYS April 1966 R. H. CAMPBELL, JR 3,247,307

RHYTHM TEMPO CONTROL SYSTEM 5 Sheets-Sheet 2 Filed Aug. 17, 1962 20;. 20h 0200mm OF NOE INVENTOR.

RICHARD H.CAMPBELL JR. BY

M, ATTORN EYS R. H. CAMPBELL, JR 3,

RHYTHM TEMPO CONTROL SYSTEM 5 Sheets-Sheet 5 ll JR I A f r W W 5 n W W n NE W 52E m9 April 19, 1966 Filed Aug. 17, 1962 INVENTOR.

w QE gig T flmfl w RICHARD H CAMPBELL JR ATTORNEYS ii ii hm 1. w mm m? 2% H W W M H H H. H HP H H April 9, 1966 R. H. CAMPBELL, JR 3,247,307

RHYTHM TEMPO CONTROL SYSTEM 5 Sheets-Sheet 4 Filed Aug. 17, 1962 QWQE INVENTOR.

RICHARD H.CAMPBELL JR. BY m,

WMH ATTORNEYS April 19, 1966 R. H. CAMPBELL, JR 3,247,307

RHYTHM TEMPO CONTROL SYSTEM 5 Sheets-Sheet 5 Filed Aug. 17, 1962 RICHARD H. CAMPBELL JR.

RHYTHM GEN.

CONTINUOUS REPETITIVE CIRCUIT f/IYUI TRIGGER AUDIO MIXER ENVELOPE DETECTOR PRINCIPAL INSTRUMENT INVENTOR.

FIG.6

BY M, W4

ATTORNEYS United States Patent 3,247,307 RHYTHM TEMPO QUNTROL SYSTEM Richard H. Campbell, .lr., Gilford, N.H., assignor, by Inesne assignments, to Seehurg Corporation, Chicago, Ill., a corporation of Delaware Filed Aug. 17, 1962, Ser. No. 217,713 12 Claims. (Cl. 84-1.03)

This invention relates generally to electrical musical instruments and more particularly to arrangements with such instruments to provide for a continuous repetitive rhythm sequence being generated at a tempo which is automatically controlled to conform to the tempo at which the instrument is played by the artist who is performing on the instrument.

The present description will be made with reference toan electronic organ as the instrument with which the automatic rhythm control is employed. It will be understood, however, that any suitable musical instrument, such as an electric guitar or the like, can be provided with the rhythm circuits and controls of the present invention to provide rhythm accompaniment to the rendition produced on the instrument.

The present invention relates to circuits of the general type for automatically controlling the tempo of a continuous repetitive rhythem system disclosed and claimed in the co-pending application of Donald M. Park entitled Tempo Control for Electrical Musical Instruments. In this application of Park general arrangements are shown for developing timing wave forms representative of both the tempo at which the principal instrument is being played by a player and the tempo or repetition rate at which a continuous rhythm section automatically generates a rhythm sequence. By suitable comparison of these timing wave forms in appropriate electronic circuits, the foregoing referenced patent application of Park provides for the development of a control signal that controls the frequency of an oscillator which in turn supplies the operating frequency to a synchronous motor. The frequency of the oscillator is accordingly varied and consequently the speed of the synchronous motor is likewise varied by the control signal and since the motor is used to drive the commutator which produces the continuous reptitive rhythm pattern, the system controls the motor speed to make the tempo of the rhythm pattern follow the tempo imposed upon the principal instrument by the player who is operating or playing the principal instrument.

The present invention provides for control of the continuous repetitive rhythm sequence and the tempo in which it is played by developing the timing and reference signals representative of the repetitive rhythm directly from the commutator employed to generate the rhythm sequence. This arrangement offers substantial economies in manufacture and improved reliability since the relations between all the signals generated is fixed relative to one another as they are all derived from the fixed pattern of a commutator. By suitably providing segments on the commutator which produce speed control signals of both increasing and decreasing characteristics in fixed reference to the pattern of the repetitive rhythm produced by the commutator, a suitable motor control signal can be developed depending upon whether the players tempo on the principal instrument is ahead or behind the beat derived from the commutator which should coincide with it. With the arrangements provided by the present invention, extreme reliability and long life in the field are achieved as well as freedom from any requirements for critical adjustment thereby making the invention practical in the home market field where substantial numbers of these instruments are used but which do not receive any particular program of preventative maintenance and may be used by relatively unskilled personnel.

Accordingly, the principal object of the present invention is to provide an improved repetitive rhythm system for a player operated musical instrument which features control of the tempo of the repetitive rhythm to correspond to the tempo at which the principal instrument is operated by the player.

.These and other objects will be apparent from the following detailed description taken in conjunction with the accompanying drawings wherein:

, FIG. 1 is a block diagram showing the overall rhythm control system in accordance with the present invention;

FIG. 2 is a schematic wiring diagram of a commutator and a portion of the matrix connected thereto with the matrix connected to a portion of the selector switch asembly provided to select different rhythm combinations;

FIG. 3 is a tone beat diagram showing the tone combinations combined for two different rhythm types;

FIG. 4a and 4b taken together are schematic wiring diagrams of the tone generator used to generate the rhythm tones;

FIG. 5 is a schematic wiring diagram of the motor control circuit; and

FIG. 6 is a block diagram of a modification.

Referring to FIG. 1, the general arrangement of the invention for use with an electronic organ provides a number of major units interconnected, the details of which will be described hereinafter. The rhythm sequence is derived from a commutator and code matrix unit 31, the

commutator thereon being driven by a DC. variable speed motor 32. The code matrix employed with the commutator hereinafter described provides thirty-four output leads 33 which contain various pulse sequences as a result of the action of the commutator and the selection performed by the matrix. The leads 33 together with supply and control leads are connected by cable 34 to a control panel 35 which may be conveniently mounted on the cheekblock of the organ keyboard. The control panel 35 provides the manually operable rhythm selector switch 36, a volume control 37 which is combined with an onofi switch for the rhythm section and a tempo control 38 which is combined with an automatic-manual switch. The volume control 37 and the rhythm on-off switch associated therewith supply at selected volume the rhythm pulse tones to an output 39 which applies the tone signals to the organ voicing assembly. The tempo control 38 and the associated automatic-manual switch provide selectively to the motor control circuit described hereinafter an overriding controllable bias for selecting the desired tempo of the rhythm sequence when automatic follow-up control is not desired.

The selector switch 36 is an 8-pole 18 position switch which supplies selectively certain ones of the outputs 33 from the code matrix to the eight rhythm tone generators of a tone generator circuit 41. The tone generator 41 generates eight different kinds of rhythm tones in the sequence corresponding to the applied input pulses at terminals 42 with the outputs of the eight tone generators combined on a single output line to supply the particular tone sequence in use to the volume control 37 and, thence, to the output 39 for reproduction as sound in the organ voicing assembly. The boats from one of the basic tone generators and one or more of the subsidiary tone generators are also applied to indicator lamp lines 44- and 45 to present a visual indication of the beats in the tempo of the rhythm section on neon lamp indicators 46 and 47 of the control panel 35.

For novelty effects an optional beat-box unit 43 may be provided with manually operable switches 49, each of which supplies an input to one of the tone generators in 3 the unit 41. With the optional unit 48 controlled by a person other than the one'playing the principal instrument, various novelty effects in the rhythm pattern being played can be added to that provided by the circuit of the invention.

A motor control circuit 51 receives a phase signal on a line 52 from the commutator and a pedal switch signal on line 53 from the pedal keyboard of an organ or from any suitable switch closure operated by the player of the principal instrument which is related to the tempo at which he is playing the instrument. when automatic operation is not desired is applied on line 54 from the tempo control 38. The motor control circuit 51 supplies a control current to the motor 32 for determining the speed of rotation of the motor 32 and thus serves to control the tempo of the rhythm pattern generated by the commutator and code matrix.

Referring now to FIG. 2 the circuit of the commutator and code matrix unit 31 will be described as connected 1 to the selector switch 36 for developing the rhythm pul'se patterns to the various tone generators in the unit 41. In FIG. 2 the motor 32 is indicated as driving a double ended rotor 61 which revolves with respect to the rings of a commutator generally designated 62. The commutator has an outer ring 63 separated into discrete segments. For purposes of reference the outer ring 63 is designated as being divided into twenty-four equiangular subdivisions with an active segment being located and isolated from the remainder of the ring at angular locations 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 20, 21, 22, 23 and 24. Certain angular positions in the outer ring 63 do not have segments, such as positions 1, 13 and 19, since pulses at these particular times are not required for any of the rhythm patterns. At certain intermediate positions designated 1 /2, 4 /2, 7 /2, etc., separate seg- I connected to lead 65, segment 3 is connected to lead 66 i and segment 4 is connected to lead 67. In actual practice the segments 4, 4 /2 and 5 would also be connected to horizontal leads in the matrix 64, but for simplicity only a limited number of connections have been shown to dem- The manual control bias onstrate the selection of two particular rhythm patterns: f

from the matrix by means of the selector switch 36 and the appropriate connections to the output of the matrix. Any basic repetitive rhythm pattern can be obtained fromv the outer ring 63 by appropriate positioning of the seg-- ments which are connected to the horizontal leads of the; corresponding matrix 64. Likewise, any suitable combination of the basic rhythm pulses can be obtained on output leads such as those shown as leads 68, 69, 78 and 71 by connection to the appropriate horizontal leads such as leads 65, 66 and 67. In order to avoid interference between multiple connections to the same horizontal leads, neon tubes '72 are employed to make the coupling connection between the horizontal and vertical leads of the matrix 64. By employing a supply voltage to the segments 1-24 of the commutator ring 63 which is greater than the striking voltage for one neon lamp 72 but is less than the striking voltage required for three such lamps in series, the matrix connections between horizontal and vertical leads can be made independently of one another since multiple paths through three or more lamps in series will not be produced upon the application of a voltage from the commutator segments due to the fact that this voltage is less than three times the striking voltage for a single lamp and all undesired paths between inputs and outputs of the matrix 64 include at least three neon tubes in series.

The voltage supplied to the outer ring 63 of the commutator 62 is obtained from a third ring 72 which is a continuous slip ring contacted by a brush 73 carried at one end of the rotor 61 and electrically connected to a similar brush 74 also connected and carried at that end of the rotor. As indicated, a lead 75 connects a positive volt supply to the slip ring 72.

Speed control signals in accordance with the invention are derived from a ring 76 on the commutator which has pairs of segments 77 and 78 which are angularly disposed. on opposite sides of index points represented by segments on ring 63 numbered 6, 12, 18 and 24. It should be noted that these index points are selected on an arbitrary basis and the position of the segment pairs 77, 78 on the ring 76 could be at other positions with the corresponding change in the relative position of wipers 81 and 82 on the rotor arm 61. The wiper 81 traverses the ring 76 making contact with the spaced segments 77, 78 in sequence for the purpose of sensing a position of the rotor 61 relative to a rhythm beat which is imposed upon the principal instrument by the player as he renders a performance on the principal instrument accompanied by the automatic rhythm tempo control system. For this purpose the wiper 81 is electrically connected to a wiper 82 which traverses a continuous slip ring 83 which supplies the phase signal on line 84. Although the term phase signal is employed to characterize the signal appearing on lead 84 in the particular disclosed system, this signal is actually merely a bidirectional voltage which is negative when the wiper 81 is on segments 77 and positive when the wiper 81 is on segments 78. The unconnected small segment appearing between the segments 77 and 78 is the neutral point at which the rhythm follow-up system is in synchronism with the beat applied to the principal instrument by the player and at this point no voltage is applied to the output lead 84. To provide these positive and negative control signals, the segments 77 are all connected in common to a negative 150 volt supply terminal 86 and the segments 78 are all connected together to a positive 150 volt supply terminal 87.

The pulse sequence produced by the turning of the rotor 61 around the outer ring 63 to contact the sectors at the numbered positions 1-24 are combined into particular pulse rhythm sequences on the vertical output leads of the matrix 64, as previously described. These pulse sequences are further combined in the selector switch 36 to provide combinations of tones irnpulsed in the particular pulse sequences which produce the desired rhythm sound. For this purpose the selection of two different sound rhythms has been illustrated using only the four vertical output leads 68-71 of the matrix 64 and two positions of the switch 36. In actual practice many more rhythm combinations can be produced by proper cross connections between horizontal and vertical leads in the matrix 64 with the total number of output leads from the matrix 64.- for a particular practical embodiment of the invention being thirty-four. For the purpose of illustrating the invention, however, the four leads 68-71 are connected as. indicated to the stator contacts of the 8-pole selector switch 36 with rotary contacts 89 of the switch 36 positioned for each section thereof in location No. 1 for" selecting a fox trot rhythm sequence and movable to position No. 2 to obtain a waltz rhythm sequence. The rotors. 89 of the eight sections of selector switch 36 are connected respectively to leads 91-98 which extend to the inputs 42 of the tone generator 41 shown in FIG. 1.

Referring now to FIG. 3 the rhythm tone combination sequence for the fox trot and waltz will be described, as selected by the portion of the selector switch 36 shown in FIG. 2. In the position shown for the selector switch, the fox trot sequence is produced and for this sequence only the base drum and wire brush tone generators are employed. As indicated in FIG. 3, line A, the base drum beat occurs at positions 0 (24), 6, 12, 18 and 24 of the commutator 62 and this beat is obtained by connecting to the appropriate segments located at these positions in ring 63 of the commutator. All of these segments 6, 12, 18 and 24, it will be noted, are connected (by ne-on tubes) to the vertical output line 69 of the matrix 64 which is connected directly to the top section of switch 36 supplying output lead 91 thereof. Thus each time the rotor 61 moves so that Wiper 74 contacts the segments in ring 63 at 6, 12, 18 and 24 positions, the 150 volt potential applied from slip ring 72 to the wiper 74 via wiper 73 is effective to fire the respective neon tube 72 which connects these segments to output lead 69. Thus an electrical pulse is applied to lead 91 for energizing the base drum tone generator in this sequence. In addition to the base drum, the wire brush tone is required in FIG. 3, line A at positions 0, 2, 3, 6, 8, 9, 12, 14-, 15, 1?, 2d, 21, and 24. This combination of wire brush and drum is characteristic of a simple fox trot rhythm and the wire brush generator connected to lead 98 is energized from the vertical lead 71 of the matrix 64 by connection to the appropriate segments on ring 63 corresponding to the numbered positions just enumerated. These connections are generally made through neon tubes in the matrix where necessary to avoid unwanted couplings. In certain instances where for the particular rhythms used in a given embodiment of the invention, cross coupling will not be a problem for particular connections and in this event the segments of ring 63 can be directly wired together. Examples of this which happen to be present in the particular rhythms used in applicants current embodiment of the invention are illustrated in FIG. 2 where segments 2, 14 and 20 are directly connected together, as are segments 4, and 22. This feature is merely a matter of economy in not requiring individual neon lamps for connection to the corresponding vertical output lea-d of the matrix 64 and does not significantly alter the general layout of the matrix on the principles hereinbefore described.

In line B of FIG. 3 the tone combination sequence for a waltz rhythm is shown. This rhythm consists of the base drum at times 0, 6, 12, 13, and 24- and accompanying the base drum on alternate beats at d, 12 and 24 is the first tom-tom. At intervals 2, d, 8, 1G, 14, 16, 20, and 22 the second tom-tom and wire brush tones are generated together. This sequence is obtained by changing the selector switch 36 in FIG. 2 to the second set of terminals, i.e., those terminals next adjacent to those indicated as connected to the rotors 89 in the drawing of FIG. 2. With the selector switch 36 so positioned, the base drum sequence is derived from line 69, as previously described. The first tom-torn sequence is derived from line 68 which is connected by neon tubes 72 to segments 12 and 24 on the ring 63 of the commutator. The second tom-tom and wire brush sequence combination is derived from line 71 of the matrix which connects by means of neon tubes 72 to the segments 2, 4, 8, 11), 1d, 16, and 2h, 22. Some of these connections such as the connections from segments 14 and 20, for example, are permanently joined to be supplied over the horizontal lead 65 of the matrix 64 since these particular segment pulses are not required independently of the others and the more economical connection which does not require multiple neon tubes can be employed.

While only two relatively simple rhythms, namely, the fox trot and waltz have been indicated as selectable by the switch 36 from the pulse sequences derived from the output leads 68-71 of the matrix 64, it will be apparent that a much more complete matrix selection can be made from the individual segments on the ring 63 to a larger plurality of vertical outputs than indicated and even further output combinations of pulses could be generated if desired. These combinations can be combined in any desired manner by suitable wiring of the selector switch 36 so that the various rhythm sequences required for the wide variety of musical compositions to be played can be provided, the only limitation being the expense and bulk involved in unduly multiplying the 6 number of available selections. Since these combinations are in a certain degree based on artistic choice, the particular combinations provided for all the different rhythms have not been described since the manner of forming such combinations can readily be seen from the teaching of the illustrated embodiment.

Referring to FIGS. 4a and 4b, the schematic circuit diagram for the tone generators will be described. Eight inputs 91', 92, 93', 94', 9'5, 9'6, 97', and 98' are connected to the corresponding unprimed numbered leads of FIG. 2 to supply the input pulse sequence for the individual tone generators. Each of the inputs 11-97 supplies an input circuit comprising voltage divider resistors 101 and 102 and a capacitor 103 connected in parallel with resistor 102. The pulses appearing across the resistor-capacitor combination 1112, 1113 are coupled through a series resistor-capacitor combination 104, 105 to a parallel resonant circuit 166. The operation of the circuits just described provide for rounding the leading edge of the voltage pulse produced from the commutator and matrix operation with the input voltage being sustained for the period of the time constant of the circuit involved due to the removal of the conductive path through the neon tube and commutator segment as soon as the wiper is removed from the commutator segment which generated the pulse. The application of this pulse to the resonant circuit 106 causes an exponentially decaying oscillation in the resonant circuit 106 which simulates the sound of the instrument intended when reproduced through the organ voicing assembly. For this purpose the resonant circuit 106 is coupled through a coupling resistor 1117 to line 108. Signals on line 108 are amplified in a triode 1M and cathode follower 111, the output of which is applied to volume control potentiometer 112. The setting of potentiometer 112 is made by control 37 as is the switch connecting the output of the potentiometer 112 to the input of a co-axial cable 35 supplying the signals to the organ voicing assembly. Degenerative feedback around the amplifier stages 109 and 111 is achieved by means of resistor 114.

The resonant circuit 166, just described, has a relatively low resonant frequency and simulates in sound the base drum whenever the circuit 1116 is energized by pulses from the network connected between resonant circuit 106 and input terminal 91. This pulse sequence is also applied to the grid of a triode 115 which is connected to the diode indicator lamp 46 located on the control panel 35 for giving a visual indication of the basic beat reproduced in synchronism with the base drum tone actuation.

Each of the additional inputs 92-97 is applied through a suitable coupling network similar to that described for the elements 161-105 for coupling the pulse sequence applied thereto to the respective resonant circuits 117, 118, 11?, 120, 121, and 122. The resonant circuits 117 and 113 have a frequency which corresponds to two distinct tones representing diiferent pitched tom-toms. The resonant circuits 119-122 have resonant frequencies which reproduce tones representing four different pitches of woodblocks. The time constants of the coupling circuits to these progressively higher pitch resonant circuits 119- 122, corresponding to elements Eli-1'85 for the resonant circuit 1%, are also of progressively shorter duration so that the input pulses to each resonant circuit are matched to the resonant frequency involved. All of the resonant circuits 117-122 are coupled through suitable resistors to line 108 for application through the amplifiers 1d) and 111 to the organ voicing assembly.

One further tone generator is provided which employs resonant circuit 123 which is used to generate two different tones. The resonant circuit 123 when energized as hereinafter described with a short duration pulse simulates the sound of the wire brush on a snare drum and when energized with a substantially longer pulse is used to simulate the sound of the cymbals.

. In order to achieve these two sounds, the resonant circuit 123 is energized from a noise generator which operates using triode 124 connected in a blocking oscillator configuration to produce a noise output at lead 125 which is coupled to the grid of a normally cut ofi triode 126. The output from the plate of triode 126 is connected to the resonant circuit 123. Capacitive leakage of the noise voltage on lead 125 through the grid plate capacitance of the tube 126 is suppressed by means of a noise filter 127 which is operative with diode 128 conductive whenever the triode 126 is cut off. Whenever a pulse sequence appears on input terminal 98', the pulses are coupled through a relatively short time constant circuit and decoupling diode 39 to the grid of triode 126 via coupling circuit 131 and thus permit noise bursts from lead 125 to be amplified in the tube 126 for the duration and sequence of the input pulses thereto. As previously stated, when these pulses are short, the energization of the resonant circuit 123 produces a sound output signal Which reproduces the sound output of the wire brush on a snare drum. A separate input 129 is provided from the beat box 49 for reproducing the sound of the cymbals. The terminal 129 is connected throught a somewhat longer time constant circuit and decoupling diodes 1911 to the resistance capacitance coupling network 131 from which it is applied to the grid of the triode 126 to permit the noise voltage on line 125 to be applied to the resonant circuit 123. For these longer pulses the audio reproduction of the noise voltage response of the resonant circuit 123 simulates the clash of cymbals. This longer time constant signal is derived solely from the beat box 49 and not included in the tones which can be derived from the commutator generated pulse sequences due to the long duration of the simulated cymbal clash since at high rotor speeds on the commutator this long duration tends to overlap subsequent generator tones and produce an undesirable sound mixture. The output of the resonant circuit 123 is connected to lead 108 'for passage to the organ voicing assembly after amplification in the stages 109, 111.

Each of the signals applied to the inputs 94-98 is also coupled to a lead 132 which supplies the grid of a triode 133 which has the neon lamp indicator 47 connected in its plate circuit. The indicator 47 indicates visually the auxiliary beats of the particular rhythm being reproduced by this portion of the system of the invention to aid the performer in using the instrument.

Each of the inputs 91-98 also has a parallel input 91%" which is supplied from individual switches 48 in the beat box 49. These inputs permit independent manual control of the generation of the various tones provided by the tone generators circuits of FIG. for the purpose of producing novelty effects or imposing a rhythm controlled by another person upon that which is produced to follow the composition as played by the player of the principal instrument.

Referring now to FIG. 5, the schematic circuit diagram of the motor control circuit will be described. The motor control speed signal is derived from a signal obtained upon closure of relay contact 135 which is operated in synchronism with the beat on the pedal keyboard of the principal instrument or a similar beat from an appropriate point in an instrument which does not employ a pedal keyboard. Two arrangements for closing the relay contact 135 are indicated in FIG. 5. The first arrangement includes a switch 136 which represents the switch associated with each pedal on a pedal keyboard which would ordinarily be periodically closed in tempo by the normal operation of the player in his rendition of any particular selection. The closure of switch 136 applies a negative potential from terminal 137 to the grid of a tube 138 which inverts the signal. The positive pulse on the plate of tube 138 is diiierentiated by capacitor 158 and resistor 157 to apply a momentary positive im- 8 pulse of fixed duration to the grid of a tube 139. The plate circuit of the tube 133 energizes relay 141 which operates the contacts 135 so that contacts 135 remain closed for an interval determined by the time constant of capacitor 158 and resistor 157 and independent of the duration of the pedal actuated switch closure 136.

As an alternative for using the system of the present invention where a pedal keyboard is not readily available, a suitable auxiliary pedal or key 142 may be provided which directly or indirectly controls the closure of switch 136 and hence of the relay contact 135, as indicated. In this instance the player would be required to keep time with the primary beat on auxiliary pedal 142 in order to operate the rhythm speed control followup system in accordance with the invention.

The relay contact 135 applies a potential through resistor 148 to the control grid of a pentode 136, the polarity of which is determined by which of the commutator segment 7'7 or 78 happens to be contacted by the brush 81 at the moment the contact 135 closes. For this purpose the lead 84 of FIG. 2 is connected to terminal 144. The tube 143 is connected as an integrator to maintain the signal applied at the control grid thereof during intervals when the grid circuit is opened. For this purpose a large low leakage capacitor 147 is connected from the plate of tube 143 to the control grid thereof. The plate of tube 143 is connected to screen grid 145 of a current control tube 146. The cathode circuit of the tube 146 includes the speed control winding of motor 32 and hence the current supplied by tube 146 directly controls the speed of the motor 32.

So long as contact 135 remains open the stored charge on this capacitor will maintain the grid and plate potentials of tube 143 constant for long periods of time. Closure of contact 135 at a time when a potential is present on terminal 144 will produce a change in grid potential at tube 143. This will in turn cause a change in plate potential at tube 143 and in the charge stored in capacitor 147. The rate of change is determined by a time constant which is the product of the resistance of resistor 148, the capacitance of capacitor 147, and the gain of tube 143. The amount of change during one closure of contact 135 will therefore be determined by this same time constant and by the time that contact 135 remains closed.

In normal operation the tempo is first set manually, by means hereinafter to be described, to some desired value and the manual setting means is then disconnected. A charge on capacitor 147 corresponding to the pre-set tempo is established and will hold until contact 135 closes. The player now starts playing in time with the automatic rhythm section, and contact 135 closes repeatedly in response to the players tempo. If the players tempo is exactly the same as the tempo of the automatic rhythm section, contact 135 will close when wiper 81 is on unenergized commutator segment between the contact segments 77 and 73. There is thus no potential on terminal 144 and hence there will be no change in the automatic rhythm section tempo. If the players tempo begins to speed up, contact will close when wiper S1 is on contact '77 and there will be a negative potential on terminal 144 when contact 135 closes. This will cause a negative voltage increment on the grid of tube 143, producing a positive increment on its plate and hence on the cathode of tube 146, increasing the motor speed and the automatic rhythm section tempo. If one closure of contact 135 is not sufiicient to correct the difference in tempos, the next closure of contact 135 will find wiper 81 again on contact 77 and there will be a further correction. This will continue until the two tempos are again alike. Conversely, if the players tempo slows down the closure of contact 135 will occur when wiper 81 is on contact 78, there will be a positive voltage on terminal 144, and a positive voltage increment on the grid of tube 143 reducing the motor speed and the automatic rhythm section tempo.

When the player is maintaining a steady tempo, there should normally be no corrective voltage increment impressed on the grid of tube 143 by closure of contact 135. However, minor irregularities may cause contact 135 to close when wiper 81 is, for example, on contact 77. This will cause a slight increase in the automatic rhythm section tempo. The change resulting from a single closure of contact 135 will, however, be barely discernible and it will increase the probability that a subsequent closure of contact 135 occurring slightly later will produce a change in the opposite direction. Thus the speed of the motor will vary slightly so that contact 135 closure occurs first when wiper 81 is on contact 77 and then when it is on contact 78 with a tendency to hunt back and forth between these two conditions without producing an audibly perceptible change in tempo.

If the players tempo is steadily increasing, a succession of closures of contact 135 will take place with a predominant proportion of them occurring when wiper 81 is on contact 77. The corrective increments will accumulate, even though each individually is very slight, and the speed change will follow a smooth transition determined by the time constant of the integration circuit of tube 143.

Similarly, a steady decrease in the players tempo will of contact 135 all occur when Wiper 81 is on either contact 77 or contact '78.

For initially setting the tempo or in the event that automatic follow-up of the tempo of the rhythm section is not required, the control 38 may be employed to close the switch contact indicated in FIG. 5 at 140 which proides for the application of an adjustable negative bias from the tap of potentiometer 149 for manual control of the speed at which the commutator rotor 61 is driven. With the switch 14%) closed, the continuous voltage supply obtained from the tap of potentiometer 149 completely overrides the signal applied from terminal 144 through contact 135.

Referring now to FIG. 6 a modification of the invention is shown for instruments in which a player operated switch actuation is either not available or not desired. A principal instrument 150 supplies an electrical signal through an audio mixer 151 to a suitable reproducer 152, which reproduces an audio output corresponding to the electrical signal applied thereto. The signal from the principal instrument 15%) is sampled by tapping at line 153. The signal on line 153 is suitably processed to detect the envelope thereof in an envelope detector 154. The peaks of this output waveform are selected relative to a self-bias threshold, for example, to operate a trigger circuit 156. The trigger circuit 156 is connected to energize relay 141' which operates contact 135' corresponding to the similarly numbered unprimed contact 135 in FIG. 5. The contact 135' is applied to a continuous repetitive rhythm generator 155 which corresponds to the system described herein with reference to FIGS. 1-5. The controlled rhythm of generator 55 is combined in mixer 151 for audio reproduction by transducer 152 with the melody from principal instrument 150. The system of FIG. 6 thus operates automatically to select from the musical composition played and reproduced by the transducer 152, as derived from the principal instrument 150, a characteristic which is repetitive at the principal beat of the composition rendered. Any suitable characteristic may be selected and the peak amplitude at a given frequency is indicated in the present disclosure as only one of those which may be selected. If the instrument reproduces in both a rhythm channel and a melody channel, it would be expedient to select the signal on lead 153 from the rhythm section of the principal instrument since synchronization of the automatic rhythm accompaniment provided by the invention with the tempo 19 at which the principal instrument is reproducing the sound is what is desired.

While a particular embodiment of the invention has been shown and described herein, many modifications thereof will occur to those skilled in the art for developing simplified reliable speed control signals related to the tempo at which an instrument is being played. Accordingly, such modifications as fall within the scope of the appended claims are to be considered within the purview of the present invention.

I claim:

1. An electronic musical instrument of the continuous repetitive rhythm type used to accompany an instrument under player control comprising a stator having multiple segments in predetermined array, an element movable repetitively over said array and operative to be coupled to said segments in sequence, circuit means coupled to said segments and said element and responsive to said element coupling to selected ones of said segments for producing a pulse train characterized by the segments selected, a second array of spaced pairs of segments with individual segments of a pair located on opposite sides of an index on said stator, coupling means movable in fixed relation to said element for traversing the segments of said pairs in sequence, a circuit coupled to said spaced pairs and said coupling means for developing a bidirectional control signal, means for combining said control signal with a signal representing the tempo at which said instrument is played by said player for selecting a direction of said control signal, and means responsive to the selected direction of said control signal for altering the speed at which said movable element and said coupling means are driven over said arrays to reduce any difference between said tempo and the tempo of said repetitive rhythm.

2. A player controlled electronic musical instrument of the continuous repetitive rhythm type comprising a commutator having a stator and rotor, a first ring on said stator having predetermined spaced segments corresponding to component beats of various rhythms, a first contact on said rotor for contacting said segments in sequence as said rotor turns, a second ring on said stator having pairs of segments with the segments of each pair angularly spaced on opposite sides of an index on said first ring, a second contact on said rotor for traversing the segments in each said pair in a sequence which contacts the first segment of a pair before and the last seg ment of the same pair after the said first contact is in predetermined position relative to said index, circuit means coupled to the segments of said first ring and said first contact for producing predetermined rhythm sound patterns as said rotor turns, variable speed drive means for said rotor, means for energizing said first and second segments respectively of each said pair with speed increasing and decreasing signals, and means for coupling said second contact to apply said speed increasing and decreasing signals to said variable speed drive means periodically according to the tempo at which said instrument is being played by said player.

3, Apparatus according to claim 2 in which the last named means includes a switch operated in response to actuation of the pedals of a pedal keyboard to connect said second contact to said variable speed drive means.

4. Apparatus according to claim 2 in which the last named means includes a manually operated switch actuated by the player of said instrument to connect said second contact to said variable speed drive means.

5. In an electronic musical instrument an arrangement for controlling the tempo of a continuous repetitive rhythm comprising a commutator having an array of spaced segments and a contactor driven to connect periodically with said segments in sequence to generate pulses corresponding to the basic beats of said rhythm, segment pairs on said commutator angularly positioned on opposite sides of index points in said array, a contact mov- 11 able in fixed relation to said contactor for traversing the segments of said pairs in sequence, means for energizing with speed increasing and decreasing signals the respective segments of said pairs in the order traversed by said contact, means for producing a periodic reference characteristic, means for sensing the speed control signal on said contact in synchronism with said periodic reference, and means for averaging the sensed speed control signals and altering the speed of the drive for said contactor in response thereto to conform said tempo to said reference.

6. Apparatus according to claim and including a matrix the input of which is connected to the segments of said array, and coupling means in said matrix for combining pulses from dilferent combinations of segments of said array to a plurality of outputs of said matrix respectively.

7. Apparatus according to claim 6 in which said matrix has a plurality of input leads respectively connected to the segments of said array and a plurality of output leads, and said coupling means are gaseous discharge tubes having the discharge paths thereof connected between said input and output leads in combinations to produce on said output leads predetermined pulse rhythm patterns, the potential difference applied to said tubes when said contactor contacts the segments of said array being greater than the breakdown voltage of one of said tubes but less than the breakdown voltage of three of said tubes in series.

8. Apparatus according to claim 7 and including a mul tiple selector switch for selectively connecting different combinations of said outputs to a plurality of individual rhythm instruments for producing said continuous repetitive rhythm.

9. In an electronic musical instrument an arrangement for controlling the tempo of a continuous repetitive rhythm to correspond to the tempo at which said instrument is playing comprising a commutator having an array of spaced segments and a first wiper driven to connect periodically with said segments in sequence to generate pulses corresponding to the basic beats of said rhythm, segment pairs on said commutator angularly positioned on opposite sides of selected ones of said segments in said array, a second wiper driven in fixed relation to said first wiper to contact the segments of each of said pairs in a sequence which contacts the first segment of a pair before and the other segment of a pair after said first wiper contacts a corresponding segment in said array, and means for deriving a speed control signal for controlling the speed at which said wipers are driven in response to the average signal on said second wiper during predetermined time intervals in successive measures of the tempo at which said instrument is playing.

10. Apparatus according to claim 9 and including manually operated means for periodically sampling the signal on said second wiper for comparing the tempo at which said instrument isplaying with the signal on said second wiper.

11. .Apparatus according to claim 9 and including means responsive to the music signal produced by said instrument for deriving a pulse signal representative of the major beat of said music, and means responsive to said pulse signal for periodically sampling the signal on said second wiper for comparing the tempo at which said instrument is playing with the signal on said second wiper.

12. In an electronic musical instrument an arrangement for controlling the tempo of a continuous repetitive rhythm to correspond to the tempo at which said instrument is playing comprising means for generating a continuous repetitive rhythm signal, means for controlling the tempo of said rhythm signal, means responsive to the electrical musical signal produced by said instrument for detecting the major beat of said electrical musical signal produced by said instrument, means for comparing the tempo of the detected major beat signal with the tempo of said rhythm signal and changing the tempo of said rhythm signal to that of said major beat, and means for producing an audio reproduction of said rhythm signal in the sound output of said musical instrument.

References Cited by the Examiner UNITED STATES PATENTS 1,324,779 12/1919 Bockisch 845 1,745,071 1/1930 Wensley 53 X 3,038,364 6/1962 Bergman 84-1.24 3,039,347 6/1962 Krauss et a1. 84-126 GEORGE N. WESTBY, Primary Examiner. 

1. AN ELECTRONIC MUSICAL INSTRUMENT OF THE CONTINUOUS REPETITIVE RHYTHM TYPE USED TO ACCOMPANY AN INSTRUMENT UNDER PLAYER CONTROL COMPRISING A STATOR HAVING MULTIPLE SEGMENTS IN PREDETERMINED ARRAY, AN ELEMENT MOVABLE REPETITIVELY OVER SAID ARRAY AND OPERATIVE TO BE COUPLED TO SAID SEGMENTS IN SEQUENCE, CIRCUIT MEANS COUPLED TO SAID SEGMENTS AND SAID ELEMENT AND RESPONSIVE TO SAID ELEMENT COUPLING TO SELECTED ONES OF SAID SEGMENTS FOR PRODUCING A PULSE TRAIN CHARACTERIZED BY THE SEGMENTS SELECTED, A SECOND ARRAY OF SPACED PAIRS OF SEGMENTS WITH INDIVIDUAL SEGMENTS OF A PAIR LOCATED ON OPPOSITE SIDES OF AN INDEX ON SAID STATOR, COUPLING MEANS MOVABLE IN FIXED RELATION TO SAID ELEMENT FOR TRAVERSING THE SEGMENTS OF SAID PAIRS IN SEQUENCE, A CIRCUIT COUPLED TO SAID SPACED PAIRS AND SAID COUPLING MEANS FOR DEVELOPING A BIDIRECTIONAL CONTROL SIGNAL, MEANS FOR DEVELOPING A CONTROL SIGNAL WITH A SIGNAL REPRESENTING THE TEMPO AT WHICH SAID INSTRUMENT IS PLAYED BY SAID PLAYER FOR SELECTING A DIRECTION OF SAID CONTROL SIGNAL, AND MEANS RESPONSIVE TO THE SELECTED DIRECTION OF SAID CONTROL SIGNAL FOR ALTERING THE SPEED AT WHICH SAID MOVABLE ELEMENT AND SAID COUPLING MEANS ARE DRIVEN OVER SAID ARRAYS TO REDUCE ANY DIFFERENCE BETWEEN SAID TEMPO AND THE TEMPO OF SAID REPETITIVE RHYTHM. 